PROJECT SUMMARY Late stage ovarian cancer is marked by poor patient survival due to metastatic spread in the peritoneal cavity. Malignant ascites in the peritoneum harbor tumor cells that exhibit adaptability to anchorage independent survival required for transcoelomic metastasis. Thus, defining key adaptation signals that support anchorage independent survival in the ascites will result in new approaches to control ovarian cancer associated mortality. We recently uncovered Sox2, a key developmental gene, as an important regulator of anchorage independent survival. Sox2?s significance in cancer is underscored by prior reports on Sox2 functions in cancer stem cells and associations with poor patient survival. Curiously, while close to 75% of ovarian tumors display SOX2 gene copy number gain, Sox2 expression does not correlate with this SOX2 amplification in tumors. The significance of SOX2 amplification to the etiology of ovarian cancer progression hence remains elusive. We now find that Sox2 is significantly elevated in a context-dependent manner in ovarian cancer upon loss of attachment and necessary for anchorage-independent survival. We have identified a previously unexplored function of Sox2 as a master regulator of mitochondrial function, an important survival adaptation in anchorage independence. Sox2 promotes mitochondrial respiration and expression of genes required for mitochondrial electron transport chain transcription and translation, and antioxidant function, including the manganese superoxide dismutase, Sod2. While Sox2?s most established role is in lineage specification during development, mechanisms by which Sox2 is regulated in ovarian cancer and promotes survival during metastasis are largely unknown. Thus, our objectives here are to define Sox2 as a convergence point of stress response pathways for mitochondrial control during ovarian cancer metastasis using a combination of in vitro and in vivo approaches. To accomplish these objectives, we will: 1) Define regulation of Sox2 under anchorage independence in the context of epigenetic regulation and metabolic and redox stress associated with loss of attachment; 2) Delineate the mechanisms by which Sox2 acts as a key regulator of mitochondrial function and quality control; and 3) Determine the necessity of Sox2-driven mitochondrial function for anchorage independent survival and metastasis. Our studies will provide significant new knowledge on the dynamic regulation and role of Sox2 in ovarian cancer. Defining the Sox2-mitochondrial axis as a key adaptation for ovarian cancer anchorage-independent survival and metastasis will be a major step in identifying key stress adaptations of ovarian cancer that can be targeted therapeutically.